Effective pure states for bulk quantum computation
- Computer Research and Applications CIC-3, MS B-265, Los Alamos National Laboratory, Los Alamos, New Mexico87455 (United States)
- Theoretical Astrophysics T-6, MS B-288, Los Alamos National Laboratory, Los Alamos, New Mexico87455 (United States)
In bulk quantum computation one can manipulate a large number of indistinguishable quantum computers by parallel unitary operations and measure expectation values of certain observables with limited sensitivity. The initial state of each computer in the ensemble is known but not pure. Methods for obtaining effective pure input states by a series of manipulations have been described by Gershenfeld and Chuang (logical labeling) [Science {bold 275}, 350 (1997)] and Cory {ital et al.} (spatial averaging) [Proc. Natl. Acad. Sci. USA {bold 94}, 1634 (1997)] for the case of quantum computation with nuclear magnetic resonance. We give a different technique called temporal averaging. This method is based on classical randomization, requires no ancilla quantum bits, and can be implemented in nuclear magnetic resonance without using gradient fields. We introduce several temporal averaging algorithms suitable for both high-temperature and low-temperature bulk quantum computing and analyze the signal-to-noise behavior of each. Most of these algorithms require only a constant multiple of the number of experiments needed by the other methods for creating effective pure states. {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 627912
- Journal Information:
- Physical Review A, Vol. 57, Issue 5; Other Information: PBD: May 1998
- Country of Publication:
- United States
- Language:
- English
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